A patient that has lost all his/her dental pieces suffers a complex biological, psychological and social disorder that directly affects his/her quality of life. The restitution of these pieces by means of removable prostheses supported on the remaining anatomical structures has been prescribed by more than 200 years, but such restitution is affected by progressive bone mass loss, which makes its stability difficult, especially in the jaw bone.
This causes a high percentage of treated patients to be unable to use their dental prostheses. This situation does not only affect our health system. Studies by Rodriguez-Baciero (Oral Health In The Elderly in Spain, Ed. EGUÍA, Bilbao, Spain, 1996) indicate that 62% of all totally edentulous (toothless) Spanish patients are not able to use their dental prostheses.
Conventional techniques limit the possibilities of treatment for a growing group of people that has serious trouble to develop an appropriate level of life.
The stability of dental prostheses was solved 40 years ago in first world countries with the use of titanium dental implants that anchor them to the bone. Such dental implants have demonstrated their predictable long term success in many studies (Adell et al., Int J Oral Maxillofac Implants, 1990 Winter, 5(4):347-59; Jemt and Lecholm, Int J Oral Maxillofac Implants, 1995 May-June, 10(3):303-11). However, the high cost of these systems, their complexity and the further requirement of multiple clinical stages to install them, and an average treatment duration of 5 months, make this alternative to be out of the scope of public health programs in developing countries.
In the last decade, provisional implants made their appearance in the US market, which has been defined as mini-implants due to their 1.8 mm diameter (versus 3.3 mm in conventional implants).
These implants are very easy to use, require few stages to be installed, have a low cost and are prescribed to provisionally rehabilitate the patient. Conventional implant treatments require 6 to 7 months to be finished, due to the number of clinical stages and the requirement of the implants to heal and to be immobile inside the bone in order to facilitate bone healing around them, which allows resisting bite forces. Inversely, mini-implants start to operate the same day of their insertion to secure provisory prostheses and do not require the patient to be toothless during his/her treatment period.
Unlike definitive implants made of pure commercial titanium (99.75% purity), these little implants comprise a titanium alloy that improves their mechanical strength (90% Ti, 6% Al, 4% V).
In 1998, American odontologist Victor Sendax patented an insertion protocol for a new mini-implant design using some features developed for definitive implants (PAT U.S. Pat. No. 6,716,030). Among them, the contact with the bone is improved, by engraving the titanium surface with citric acid and using a ball-shaped prosthesis retention fixture. These features have made it the only implant to be allowed in USA by FDA to be commercialized as a transitory implant and for semi-permanent treatment (ongoing treatment).
Said implant is hanged from the head using a plastic device and is manually located in the previously prepared place. No incision is required. This causes the recovery time to be shorter and the blood loss during the procedure to be minimal, and also produces a better adaptation of the prosthesis in the same appointment; however, the disadvantage is the total dependence of the insertion of these implants on the ability of the operator and the special care that has to be applied to maintain the implant angle and to allow the bite forces to be parallel to the major axis of the implant. A direction change could cause failure due to excessive force.
Prostheses secured using these implants are immediately mounted on retention capsules (made of silicone) on the rounded head of the implant. This allows a minimal retention of the prosthesis to avoid its movement to cause implant forcing during early bone healing stages; the disadvantage of the system is the requirement of these capsules to be changed at least once every four months to attain proper retention, and also four separate implants have to be inserted to retain one prosthesis.
To these operational difficulties, an important number of in vitro studies add to assess the risk of using implants with such a small diameter, as their small contact area with the bone would receive excessive strain generated by mastication forces that could cause the implant to detach.
The present invention by using a 3D surgical guide, provides a very precise standardized protocol, splinting two of these implants by means of a prosthetic retention bar, in such a way that the total sum of both contact areas with the bone allows to obtain the same results of a large diameter implant, but with more advantages.